Arrangement for the suspension of wheels in a working machine

ABSTRACT

An arrangement of the suspension of wheels of a working machine moving on a terrain. The arrangement comprises a pair of wheels arranged next to each other to support a frame part placed on a center line between the wheels suspensions between each wheel and the frame part, wherein each suspension comprises a lower suspension arm and an upper suspension arm which lower suspension arms are mounted by means of first joints to the frame part using first joints and to mounting arms using second joints in which the wheels are mounted in a rotatable manner, and which upper suspension arms are fixed by means of third joints to the frame part and by means of fourth joints to the mounting arms. The wheels are arranged to be turnable around a substantially vertical axis, and the wheel is arranged to be turned by means of a cylinder actuator coupled between the mounting arm the wheel. In an embodiment of the invention, the first joint and/or the third joint in each suspension is placed on the center line or farther than that.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an arrangement for the suspension of wheels ina working machine movable on a terrain.

2. Description of the Related Art

For harvesting, working machines are known which move on a terrain bymeans of wheels, including harvesters in which a harvesting device isprovided at the end of a boom assembly, a so-called harvester head forcutting and felling a tree stem and sawing it to pieces of desiredlength. The sawn tree stems are collected by a loading apparatus, i.e. aforwarder equipped with a grapple, and transported in the load space.

Publication WO 89/00928 discloses a working machine which comprises twoframes connected to each other by means of a joint. The joint is used tocontrol the direction of motion, wherein the working machine is providedwith articulated steering. A swivel base is mounted on the frame toswivel around a vertical axis and is equipped with a cabin and, by itsside, a boom assembly, a harvester head being mounted at the end of theboom assembly. In a known manner, the boom assembly can also be mountedin front of the cabin or on a swivel base separate from the cabin. Inforwarders of prior art, one of the frames is equipped with a load spacewhere the tree stems are collected from the ground by means of a grapplemounted on the frame. The other frame is equipped with a cabin and apower source for the working machine. So-called combined machines arealso known, combining the functions of a harvester and a forwarder. Inthis case, for example, the rear frame in the harvester is equipped witha load space. The advantage is that the harvesting and the collection ofthe tree stems can be performed simultaneously, wherein the need forseveral machines in the forest is reduced, which also reduces damagecaused to growing stock.

For example in forest thinning, several growing trees are left by theside of the logging road used by the working machine, which limits thespace available for the working machine, particularly in the widthdirection. In the working machine according to the WO publication, thesuspension of wheels is implemented with a joint parallelogramcomprising articulated, parallel upper and lower suspension arms. Acylinder for controlling the position of the wheel is coupled betweenthe joint of the upper suspension arm on the frame side and the joint ofthe lower suspension arm on the wheel side. The joint parallelogram alsokeeps the wheel vertical in different positions.

The suspension of wheels according to prior art is problematicparticularly when there is a need to limit the dimensions of the workingmachine, particularly its width and height, without affecting the otherproperties, particularly the capability to proceed on the terrain. Theproblem is that the cylinder is mounted at a point where the pistonstroke of the cylinder becomes very long for moving the wheel from theupper position to the lower position. For this reason, the arms alsobecome long, to fit the cylinder in between, both short and long, whichaffects particularly the width of the working machine, and it isparticularly difficult to make the long suspension arms steadfast.

Another problem is that when there is a need to reduce the width of theworking machine, the moment arm of the cylinder must be made shorter,wherein said suspension arms must be made shorter. The moment arm isformed by the transverse distance between the cylinder and the joint ofthe lower suspension arm on the frame side. Reducing the length of thesuspension arms will also cause that the play between the upper positionand the lower position is reduced. In particular, the moment arm isreduced when the joints of the lower and upper suspension arms on theframe side are brought closer to each other to limit the height of theframe. The reduction of the length of the tension arm increases thepower required of the cylinder, leading to a larger cylinder and/or ahigher pressure level, which is not always preferred. Consequently, amodification of the presented wheel suspension, particularly amodification of the length of and distance between the suspension arms,will strongly affect the moment arm, wherein it is difficult to modifythe structure, particularly the mountings.

It is an aim of the present invention to eliminate the above-presentedproblems by means of a wheel suspension without increasing the width ofthe working machine, decreasing the steerability and complicating theconstructions.

The main principle in the invention is that the corresponding joints ofthe joint parallelograms of the wheels placed on different sides of theframe, on the frame side, are placed on the same axis of rotation. Inother words, the joints of the upper suspension arms are placed on thesame axis of rotation and/or the joints of the lower suspension arms areplaced on the same axis of rotation. The rotation axes are preferablyplaced on the centre line of the working machine. Thus, the width of theworking machine can be reduced, particularly at the location of thewheels, without reducing the length of the moment arms and in comparisonwith the prior art. Without affecting the width, the working machine canalso be equipped with wider tyres, or the wheels can be equipped withlarge turning cylinders for steering the wheels.

Another central principle of the invention is that the width of themachine can be further reduced in such a way that at least some of thejoints on the frame side, preferably the joints of the suspension armspairwise, are placed on the other side of the central line, opposite tothe wheels. The suspension arms are thus placed diagonally with respectto each other and seen from the direction of the rotation axis. Thejoints of the other suspension arms can thus be located on the centralline or closer to the wheel. With this arrangement and the same machinewidth, it is possible to achieve a longer adjustment of the wheels inthe height direction or a smaller dish of the wheels. In prior art, thejoints and the wheels are located on the same side of the centre line.

By placing the cylinder in a vertical position and mounting its one endto the lower suspension arm and its other end to the frame, it ispossible to reduce the piston stroke of the cylinder when compared withprior art. However, the moment arm of the cylinder can be keptsubstantially the same as in prior art, but the mounting point in thelower arm can be shifted closer to the frame. Thus, there will be morespace for other structures at the outermost end of the suspension arms.Thanks to the shorter piston stroke, the vertical cylinder does notharmfully increase the height of the structure. As the mounting point isplaced in the suspension arm and not in its joint, a change in thelength of the suspension arm will not necessarily affect the structureof the cylinder, the pressure levels used, or particularly the momentarm. With the vertical position, also the moment arm formed by thesuspension arms in different positions will be less changed when thewheel moves up and down.

It is also an aim of the invention to provide a compact module structurefor the wheel suspension and the frame structure in various workingmachines.

In the following, the invention will be described in more detail byusing as an example an advantageous embodiment of the invention withreference to the appended drawings, in which

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the structure of a joint parallelogram in a reduced viewand the suspension of a cylinder seen from the direction of the rotationaxis,

FIG. 2 shows a module according to an advantageous embodiment of theinvention in a perspective view in the middle position of the wheels,

FIG. 3 shows the module of FIG. 1 in the upper and lower positions ofthe wheels, and

FIG. 4 shows the module of FIG. 1 in the lower position of the wheels.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1 and 2 illustrate an arrangement according to the invention forthe suspension of wheels. FIG. 1 shows, in a reduced view, one jointparallelogram applied in the invention, and its different arms in themiddle position. FIG. 1 also shows the positions of suspension arms 6 aand 7 a and a cylinder actuator 12 a for controlling the position of amounting arm 5 a in the vertical direction. A wheel is mounted to themounting arm 5 a as shown in FIG. 2. For comparison, the prior artplacement of a cylinder C is also illustrated with a broken line. If thesuspension arms of the joint parallelogram are parallel and equal inlength, the position of the mounting arm and thereby the position of thewheel are changed as little as possible in the different positions ofthe joint parallelogram. Normally, the arms are unequal at least inlength.

With reference to FIG. 2, the arrangement according to the inventioncomprises a frame part 1 placed on a vertical central line CL andforming part of a frame in a working machine intended to move on aterrain, such as a harvester, a forwarder or a combined machine. Forexample, a working machine for handling and transportation of timbercomprises a front frame and a rear frame arranged to be movable by meansof one or several pairs of wheels. The wheels are connected to the frameby means of a suspension according to the invention. The front frame isalso equipped with a power source for the working machine, typically adiesel engine. The working machine is equipped with a mechanichydrostatic transmission system.

Onto the front frame, a swivel base is mounted, onto which are alsomounted a cabin and a boom assembly. The boom assembly is arranged forexample in front of the cabin, and the end of the boom assembly can beconnected to a tool, such as a harvester head. The frames are connectedto each other by means of a joint which allows the turning of the frameswith respect to each other around an axis in the longitudinal directionof the frame. Furthermore, on the rear frame, a load space is providedfor the transportation of timber, such as delimbed and cut tree stems.

The arrangement according to FIG. 2 is further equipped with twosubstantially U-shaped bunks which are mounted on the frame part 1,wherein it forms part of said rear frame. A corresponding constructionwithout the bunks can constitute a part of the front frame. The frontend of the rear frame is also equipped with a timber shield whichprevents timber loaded in the load space from gliding and colliding withthe cabin. The timber shield and the bunks can also be arranged to beremovable, to modify the load space.

The frame part 1 is supported by wheels 2 a and 2 b placed on its eachside. The wheels 2 a and 2 b are normally pneumatic rubber tyres fittedon a removable rim. The rim is mounted, in a rotatable manner, onbearings, and in a way known as such, on a wheel centre which isequipped with a motor, known as such, for rotating the rim with thewheel and thereby to move the working machine. The wheel rotates arounda substantially horizontal axis. Furthermore, the wheel centre isarranged to rotate around a substantially vertical axis, wherein thedirection of movement of the working machine can be controlled bysteering the wheel. The wheel centre is rotated by means of cylinders 4a driven by a pressurized medium. The arrangement comprises asubstantially vertical mounting arm 5 a where also the joints 3 a and 3b are arranged.

The mounting arm 5 a is mounted to the frame by means of an uppersuspension arm 6 a and an upper suspension arm 7 a, which aresubstantially parallel. Each suspension arm 6 a, 7 a is mounted to themounting arm 5 a by means of a joint 8 a or 9 a, the joints allowing therotation of the suspension arm in relation to the mounting arm around asubstantially horizontal axis. Each suspension arm 6 a, 7 a is mountedto the frame 1 by means of a joint 10 a or 11 a, the joints allowing theswivelling of the suspension arm around a substantially horizontal axis.The suspension arms 6 a and 7 a as well as the joints 8 a, 9 a, 10 a and11 a constitute a parallelogram-like structure, wherein in spite of theswivelling of the suspension arms, the mounting arm remainssubstantially vertical and the wheel 2 a remains substantially in thesame position, elevated to a different height. To increase the groundclearance, the wheel centre is mounted close to the lower part of themounting arm, and the suspension arms are mounted close to the upperpart of the mounting arm.

According to an advantageous embodiment of the invention, the suspensionarms 6 a and 6 b, placed on each side of the frame 1, are arranged toswivel around the same axis R1, by means of joints 10 a and 10 b,respectively. The joints 10 a and 10 b are thus preferably placed onsaid centre line CL. The joint 10 b of the suspension 1 b corresponds tothe joint 10 a of the suspension 11 a, and the suspensions correspond toeach other also in other respects. The wheels 2 a and 2 b are preferablyspaced by the same distance from the centre line CL, and thecorresponding arms of the different suspensions are preferably equal inlength, wherein the suspensions of the wheels operate in the same way.Correspondingly, the suspension arms 7 a and 7 b, placed on each side ofthe frame 1, are arranged to swivel around the same rotation axis R2, bymeans of joints 11 a and 11 b, respectively. The joints 11 a and 11 bare thus preferably placed on said centre line CL and above the joints10 a and 10 b.

The more detailed structure of the joints may vary within the scope ofthe invention, but in the structure of FIG. 2, the joints 10 a and 10 bas well as the joints 11 a and 11 b are further placed one after theother in the direction of the axes R1 and R2. Thus, the suspension armson different sides of the frame 1, for example the suspension arms 6 aand 6 b, are placed on different lines, wherein they can also be placeddiagonally. For moving the suspension arms 6 a and 6 b, an actuator 12 aoperated by a pressurized medium, preferably a hydraulic cylinder, iscoupled between the frame 1 and the lower suspension arm 6 a, by meansof joints 13 a and 14 a. The cylinder 12 a is mounted above the uppersuspension arm 7 a and substantially in the vertical direction. Thecylinder 12 a is mounted between the joints 8 a and 10 a, wherein thecylinder 12 a is placed in the free space between the frame 1 and themounting arm 5 a. By means of the actuator 12 a, the suspension 1 b isheld in a desired position to support the frame 1 at a desired height.By means of the actuators 12 a and 12 b of the suspensions 1 b and 1 b,the frame 1 can also be kept horizontal on an uneven terrain. With thearrangement according to the invention, it is possible to reduce thetotal width of the working machine and thereby the module M according toFIG. 2.

According to an advantageous embodiment of the invention, the joint 10 aof the suspension arm 6 a, and its axis, are placed at a determineddistance on the left side of the centre line CL. The joint 10 b of thesuspension arm 6 b, and its axis line, are placed at a correspondingdistance but on the right side of the centre line CL, wherein thesuspension arms 6 a and 6 b can move diagonally. By this arrangement,the total width can be further reduced. Without reducing the width, itis, however, possible to increase the moment arm of the cylinder withoutchanging the mounting points of the cylinder. For the simplicity of theconstruction, the suspensions preferably comply with FIG. 2, wherein theaxes are joined and placed on the centre line CL. Accordingly, the widthof the frame 1 can be made as narrow as possible, particularly at thejoints 10 a, 10 b and 11 a, 11 b.

The frame part 1 of the module M can be made in a desired length,wherein it can be directly connected to another corresponding module Mto form the frame of the working machine. The module M can also beconnected by means of a frame connector to another module M.

To illustrate the operation of the suspension of the wheel according tothe invention, FIG. 3 also shows the left wheel 2 b in its uppermostposition, wherein the cylinder 12 b is steered to its shortenedposition, and the right wheel 2 a is in its lowermost position, whereinthe cylinder 12 a is steered to its elongated position. In the presentedmanner, the frame 1 can be kept in balance, if the wheel 2 b hits a bumpon the terrain or if the wheel 2 a hits a pit on the terrain. In FIG. 4,both of the wheels 2 a and 2 b are shown in their lowermost position,wherein the ground clearance of the working machine can be increased byadjusting the suspension.

The invention is not limited solely to the above-presented embodiment,but it can be modified within the scope of the appended claims.

1. An arrangement for the suspension of wheels of a working machinemoving on a terrain, the arrangement comprising a pair of adjacentwheels arranged to support a frame part placed on a center line betweenthe wheels, suspensions arranged between each wheel and the frame partto elevate and descend each wheel with respect to the frame part,wherein each suspension comprises a lower suspension arm and an uppersuspension arm, which lower suspension arms are mounted by means offirst joints to the frame part and by means of second joints to mountingarms in which the wheels are mounted in a rotatable manner, and whichupper suspension arms are fixed by means of third joints to the framepart and by means of fourth joints to the mounting arms, wherein thewheels are mounted to the mounting arm in a turnable manner, whereinthey are arranged to be turnable around a substantially vertical axis,and the wheel is arranged to be turned by means of a cylinder actuatorcoupled between the mounting arm and the wheel.
 2. The arrangementaccording to claim 1, wherein the first joints and/or the third jointsare arranged to be swivelled around the same axis.
 3. The arrangementaccording to claim 1, wherein the first joints and/or the third jointsof the suspensions are arranged one after the other in the longitudinaldirection of the frame part.
 4. The arrangement according to claim 1,wherein a cylinder actuator for lifting and descending the wheel ismounted between the lower suspension arm and the frame.
 5. Thearrangement according to claim 4, wherein the cylinder actuator ismounted by means of a joint to the lower suspension arm between thefirst joint and the second joint.
 6. The arrangement according to claim1, wherein in each suspension, the first joint and/or the third joint isplaced on said center line.
 7. The arrangement according to claim 1,wherein in each suspension, the first joint and/or the third joint isplaced farther than said center line.
 8. The arrangement according toclaim 1, wherein each wheel is provided with a hub motor, driven by apressurized medium, to rotate the wheel.
 9. The arrangement according toclaim 1, wherein the frame part is arranged to form a part of the frameof the working machine, consisting of module structures.
 10. Thearrangement according to claim 1, wherein the working machine is atleast one of a harvester or a forwarder, intended for the handling oftree stems.
 11. The arrangement according to claim 2, wherein the firstjoints and/or the third joints of the suspensions are arranged one afterthe other in the longitudinal direction of the frame part.
 12. Thearrangement according to claim 2, wherein in each suspension, the firstjoint and/or the third joint is placed on said center line.
 13. Thearrangement according to claim 3, wherein in each suspension, the firstjoint and/or the third joint is placed on said center line.
 14. Thearrangement according to claim 11, wherein in each suspension the firstjoint and/or the third joint is placed on said center line.
 15. Thearrangement according to claim 3, wherein in each suspension, the firstjoint and/or the third joint is placed farther than said centre line.16. The arrangement according to claim 4, wherein each wheel is providedwith a hub motor, driven by a pressurized medium, to rotate the wheel.17. The arrangement according to claim 9, wherein the working machine isat least one of a harvester or a forwarder, intended for the handling oftree stems.
 18. An arrangement for the suspension of wheels of a workingmachine moving on a terrain, the arrangement comprising a pair ofadjacent wheels arranged to support a frame part placed on a center linebetween the wheels, suspensions arranged between each wheel and theframe part to elevate and descend each wheel with respect to the framepart, wherein each suspension comprises a lower suspension arm and anupper suspension arm, which lower suspension arms are mounted by meansof first joints to the frame part and by means of second joints tomounting arms, in which the wheels are mounted in a rotatable manner,and which upper suspension arms are fixed by means of third joints tothe frame part and by means of fourth joints to the mounting arms,wherein the wheels are mounted to the mounting arm in a turnable manner,wherein they are arranged to be turnable around a substantially verticalaxis, and the wheel is arranged to be turned by means of a cylinderactuator coupled between the mounting arm and the wheel, and wherein ineach suspension, the first joint and/or the third joint is placed onsaid center line.
 19. The arrangement according to claim 18, wherein thefirst joints and/or the third joints are arranged to be swiveled aroundthe same axis.
 20. The arrangement according to claim 19, wherein thefirst joints and/or the third joints of the suspensions are arranged oneafter the other in the longitudinal direction of the frame part.